Analytical balances have been proposed including means for arresting the weighing assembly of the balance, which assembly comprises, for example, a balance beam supported on a knife edge. The purpose of the arresting device is to protect the beam from jolts or impact loadings when the weighing assembly is not in its operative condition for weighing and the device includes an arresting mechanism which can be moved, by at least one operating element, into its beam-arresting condition.
However, such balances may be of widely varying constructions and modes of weighing operation. For example, in many kinds of balances the balance may have compensation means or substitution weights which are brought into operation in order to increase the weighing range of the balance. The weights may be simple mechanical weights which are selectively switched into an operative position in order to change the weighing range of the balance so as to include therein the weight of the article or material to be weighed, or alternatively, in the case of purely electrical balances the weights are formed by switchable current stages. With this arrangement, when the balance has a seven-segment display for displaying at least some weight decimals, the seven-segment display can be a part of the weighing result, or when the switchable weights are in their operative condition, it can be the entire weighing result. The fine weighing range, without the compensation weights, can be a range of inclination movement of, for example, the balance beam, the angle of beam inclination which is dependent on weight being sensed by way of code tracks, resulting in the supply of signals which are thus proportional to the weight to be measured; the display is thus actuated in response to said signals to display the weight determined by the balance. Alternatively, the balance may have electromagnetic compensation means in which the weight to be determined is counteracted by an electromagnetic assembly the current flowing therein thus representing a measurement of the weight to be determined.
In the case of balances with additional or compensation weights, as mentioned above, the arresting device can have a coarse or pre-weighing position in which the weighing assembly is partly arrested, and the arresting device can be actuated by hand by means of an actuating element such as cam discs, although more convenient balances often include a servo motor which is controlled, for example, by means of press keys.
In a balance with a seven-segment display, there is always the problem of monitoring or checking the operation of the segments in order to avoid defective readings caused by the failure of one or more segments. It has been previously proposed that a separate press key may be provided on the housing of the balance or on a control member, such separate press key when actuated causing all the segments to be simultaneously illuminated for monitoring purposes. This construction however, presupposes a deliberate intention on the part of the operator to carry out such a monitoring operation.
Another previous proposal is that of activating all the segments for a short period, such as a few seconds, when the balance is switched on. A disadvantage of this is that when the balance is used in conditions such that it is switched on, for example, only once in a day, perhaps because of the warming-up time required to be observed when first switching on, and then remains on until the end of the day, there is no further monitoring of the segments unless it occurs to the operator now and then to switch the balance on and off in the course of his working day.